Driver's Seat Ergonomics - Unfair Takes A Seat

The Project Unfair Camaro gets closer to completion as we focus on the ergonomics of the cockpit

Editor's NoteThis month's story about the fabrication and ergonomics of our Project Unfair's pedals, seat, and steering column takes place back at II Much Fabrication in John Parsons' small shop. --Jim Campisano

With the Coast Chassis Design rollcage installed, Frank Serafine (of Prodigy Customs) and I needed to get the ergonomics of our '69 Camaro in order. Since we've moved the firewall, raised the floor, made a custom transmission tunnel, and installed a rollcage, this is no simple bolt-in deal. Getting all the controls into comfortable reach and incorporating proper safety methods is no easy matter. The relationships between the seat, steering wheel, and pedals are not that obvious and something most of us take for granted when we jump into our factory-built cars. With all the changes to the surfaces in the driver's area, we had to start our positioning of the driver's controls at the beginning.

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The pedal/steering wheel/seat arrangement is a bit interdependent, but you have to start somewhere. In general (with an inch or two of tolerance), the most ergonomic performance driving position has the seat back tilted at least 15 degrees, with the steering wheel centered with the seat. The best racing position has the driver's hands at the 9-and-3 position and close enough so that the either arm can be extended over the top of the steering wheel with the wrist resting on the top of the wheel without the shoulders coming away from the seat.

From there, the pedals should be positioned with the brake pedal centered under the column, and the clutch pedal between 4 and 5 inches away (measured from the centers of the pedal pads). It's often more comfortable for the clutch to be an inch or so higher than the brake. We're going to road race this car (a lot!), and that means the throttle needs to be reachable while braking for heel-toe downshifts. That will require the throttle to be within 4 inches of the brake and about midway through the brake pedal's travel. The idea is to be able to blip the throttle with the side of your foot while maintaining threshold braking with the ball of your foot. The brake and clutch pedals should be largely controlled by your legs, while the throttle is controlled by your ankle, which is why the brake and clutch pedals are closer to you than the throttle.

That's a lot of interdependent variables, without even taking driver preferences into play. The chances of getting all this right the first time are pretty slim. Frank and I are about the same height with similar body types, but we still need some adjustability in order for the two of us to be comfortable driving the car. Most factory cars take that into account with adjustable seats, but that's not an option for us since the six-point Schroth Racing harness has very specific mount points. The only solution, since the seat is fixed into place, is to make the pedals adjustable.

We'll be using Cobra Suzuka Pro seats. (The Pro means "middle-aged man" as it is 2 inches wider in the "butt-dyno" area.) The Suzuka is an FIA-approved fixed-back racing seat but uses advanced materials for driver comfort and style. It is also designed for use with a six-point harness. We chose a fixed-back seat since there is no backseat and no need to tilt the seat back forward. It's also smaller and lighter.

The pedal set comes from Wilwood (as do the master cylinders and brakes), though our unique firewall and the need for adjustable pedals means we have to modify their setup somewhat. Only Wilwood has all the various pedal sets and balance bars we needed to get adjustable pedals with perfect ergonomics and their track-proven performance. A balance-bar setup is heavily used for circle track racing because it allows different master cylinders to be used on front and rear brakes with adjustment of the relative pressures between them at each position of the brake pedal. It's a great option for use on the street for the same reason: optimum tuning of master cylinder and caliper piston diameters for each end of the car.

MORE PHOTOS

1. The end of the story. The pedals are positioned in human-reachable form, the column is centered to the seat, and the Stack dash display is completely visible through the steering wheel.

1 The end of the story. The pedals are positioned in human-reachable form, the column is centered to the seat, and the Stack dash display is completely visible through the steering wheel.

2 A quick aside: These Cleco reusable rivets make short work of assembly and disassembly, especially with sheetmetal panels.

3 It is vital to get the steering column centered with the seat. With all the factory brackets in Camaro heaven, we had to start from scratch.

4 With the steering column mocked up in its centered position, the next thing is to put the brake pedal directly under the column.

5 The column/firewall interface is next. Again, keeping the column position at the center of the seat and at 90 degrees to the dash insert, we then find the position where it goes through the firewall.

6 A look from the engine side of the firewall. This is the center point of the column where it comes through the firewall.

7 After drilling the hole for the column, and passing it through the firewall ...

8 ... position the steering wheel end with a custom steering wheel positioning tool. It only looks like a jackstand.

10 We replace the jackstand with these welded-in brackets that attach to the cowl (like the factory) and the rollcage. This method of hanging the column fixes it in place in all three planes.

11. With the column fully positioned, it’s time to make seat brackets to put the seat where it was mocked up.

12 The seat bracket is attached to the rollcage with nominal spacers to hold it at the right height. The reason we attach it to the rollcage is to keep the seat from tearing apart in the event of an accident. It’s better if the seat moves where the rollcage goes in that unfortunate scenario.

13 With the basic frame for the seat worked out, next up is to make some brackets for it. A Sharpie is used to sketch the shape of the front seat bracket.

14 The bracket is rough-cut to shape with a bandsaw.

15 A belt sander is used to remove the saw marks and make a smooth radius.

16 It’s a lot easier to work on seat brackets on a bench instead of in the car! So, after carefully marking the seat angle and position (both sideways and forward and backward), the seat is mocked up and the brackets fitted and welded into place.

17 Here’s the seat in its final position. It’s level from side-to-side with a back angle of 20 degrees for the most comfort. The seat is very close to the floor, which was caused by moving the floor up inside the car, plus reserving enough headroom to wear a helmet comfortably.

18 All the brackets and mounts are reinforced. This car is supposed to go 200 mph, and keeping the seat secure is a very important part of driver safety.

19 The rear seat bracket goes downward to give as much seat back angle as possible. This is a change from the original design (see sidebar).

20 Now it’s time for pedals with the column and seat brackets completed. This is a bit of an awkward angle (it’s taken at about where the rearview mirror will be), but it shows how the brake pedal mount is bolted between the column bracket and the Wilwood master cylinder frame. The rod end hanging down is what attaches to the pedal. The distance between the rod end centers is easy to change and allows for pedal-height adjustment, as do the three small holes in the pedal mount tube. With a fixed seat, pedal-height adjustment is a must.

21 Another view of the brake pedal mount. The cage passes right through the pedal area, causing a lot of fabrication to work around it.

22 We’re looking at the brake pedal linkage up close. The quick and dirty aluminum adapter block and washers will be replaced with a custom Bryce Baumgart billet piece for the final setup. Also notice how the attachment of the linkage rod was moved slightly (about 5/16 inch). This was necessary to restore Wilwood’s recommended 6.25:1 pedal ratio.

23 The clutch pedal hanger attaches to the rollcage tube, to the brake pedal mount, and (behind the cage tube) to the master cylinder frame. You never know when a tube bender will come in handy.

24 Along with the Lokar throttle pedal and the ididit column, the Wilwood pedals are positioned well for good clutch control and heel-toe downshifting. When the car is more complete, it will be time to do the final pedal fitting for each of the drivers.

25 Here’s how it all turned out on the firewall side. Borgeson steering U-joints and splined intermediate shaft make for an attractive and strong package. The Wilwood remote masters will be easy to reach for the frequent brake bleeding all the track time will require.

Project Unfair Camaro is under the knife again. This time the 1969 Chevy Camaro is getting equipped with a new traction control system. Only at www.superchevy.com, the official website for Super Chevy Magazine. » Read More